The present invention relates generally to memory systems, and more particularly to memory systems with a row write, column read arrangement.
A variety of applications use memory in conjunction with other circuitry to provide different device functionality. In many cases, such memory is utilized by a processor device configured to execute software that may use the memory in connection with program execution. In other instances, specialized hardware may be used to provide logical operations and/or the like in a manner that may be faster than that provided by software executing on a general purpose processor. In addition, it is known to combine a general purpose processor with specialized hardware in some applications.
One area where such a combination of hardware and software is often used is in wireless communication devices, such as mobile terminals and position location receiver devices, such as Global Positioning System (GPS) receivers. There are a variety of applications in such devices where it may be important to recognize a pattern in received communication signals, such as transmissions from a base station of a wide area cellular mobile telecommunications network for a mobile terminal or from a GPS satellite for a GPS receiver. It may be desirable in such devices to recognize a pattern rapidly while the signal is being received or to acquire a service and/or position determination rapidly to provide greater perceived value to a user of the device. Accordingly, it is known to use digital signal processor (DSP) or the like in such devices.
The GPS location approach generally uses location services not associated with either the uplink or downlink signals used in the mobile telecommunications network. In a typical GPS application, the GPS receivers collect and analyze ranging measurements from signals transmitted by GPS satellites having known locations.
As illustrated in FIG. 1, GPS is a space-based triangulation system using satellites 42 and GPS control computers 48 to measure positions anywhere on the earth. GPS was first developed by the United States Department of Defense as a navigational system. The advantages of this navigational system over land-based systems are that it is not limited in its coverage, it provides continuous 24-hour coverage, which may be highly accurate regardless of weather conditions. In operation, a constellation of 24 satellites 42 orbiting the earth continually emit a GPS radio signal 44. A GPS receiver 46, e.g., a hand-held radio receiver with a GPS processor, receives the radio signals from the visible satellites and measures the time that the radio signal takes to travel from the GPS satellites to the GPS receiver antenna. By multiplying the travel time by the speed of light, the GPS receiver can calculate a range for each satellite in view. Ephemeris information provided in the satellite radio signal typically describes the satellite's orbit and velocity, thereby generally enabling the GPS processor to calculate the position of the GPS receiver 46 through a process of triangulation. It is known to include a GPS receiver 46 in a mobile terminal to provide position location functionality to the mobile terminal.
The radio signal 44 generally provides a location determination signal to a GPS receiver by including a unique color code pattern, referred to as a C/A code, that is associated with a particular GPS satellite 42. In other words, different GPS satellites 42 are provided different color codes. A time of flight of a radio signal 44 from a GPS satellite 42 to a GPS receiver 46 may be determined by determining a period and phase of the color code as received at the GPS receiver 46 when the GPS receiver 46 and GPS satellite 42 share a common time reference. Determining a time of flight typically includes determining a code period (i.e., a number of entire “chips” of the color code delay) and a code phase (i.e., the fractional part of a partial “chip” delay) based on characteristics of the C/A code, defined for GPS as 1023 chips/millisecond. However, doing so requires that a pattern associated with a GPS color code first be located and detected in a received signal before a time of flight can be estimated based on a determined delay. Operations for detecting a color code typically require that a plurality of samples be taken from a received signal and energies be accumulated in the process of detecting what color code pattern is present and where the repeating color code pattern starts in the received signal.
Pattern detection also may be used in other communication applications, such as code division multiple access (CDMA) communication systems, where signal energies are spread across a range of frequencies using a spreading code.